The present invention relates to fixer materials which can be used in cationic polymeric fixers in inkjet printing and which contain a marker which makes the fixer detectable when the fixer is printed on a media surface.
Dye-based ink-jet inks have become a dominant technology in the ink-jet ink arena. However, as many dyes are water-soluble, images printed using many of such dye-based ink jet inks are not as waterfast as may be desirable. The waterfastness and durability of an anionic dye-based ink-jet ink printed on media has been shown to be enhanced by overprinting or underprinting the printed image with a fixer, preferably from a separate pen. Fixers have been used to crash out anionic dye molecules by changing the pH of the printed inkjet image or by adding salts such as Ca2+ and Mg2+ to the printed inkjet image to crash the colorants, e.g. anionic pigments or carboxylated dyes. These fixers had the disadvantages of lacking durability, of causing pen wear and tear and corrosion due to the high salt content and the low pH.
More recently, cationic polymers have been used in the fixer. Thus, when the cationic polymer and the anionic dye contact one another on a substrate, a reaction between the dye and the polymer creates an image with improved durability and waterfastness. Inkjet images with improved waterfastness and durability can therefore be obtained by underprinting or overprinting a printed inkjet image with a cationic polymeric fixer.
Fixer solutions are often transparent and thus invisible when printed on a medium substrate. This has necessitated the inclusion of markers or indicators so that nozzle health, pen alignment and dot placement of the fixer can be evaluated. With only weakly cationic fixers, traditional UV and near-IR indicators like Stilbene and Tinolux BBS have been used. These are anionic, sulfonated markers visualized with UV and near IR light. Such anionic indicators react with cationic polymers and thus cannot be used in a cationic polymeric fixer.
The present invention relates to a method of detecting a cationic polymeric fixer material present on an inkjet printed media, comprising
a) inkjet printing the cationic polymeric fixer material onto a media substrate;
b) exposing the printed media substrate with ultraviolet or near IR light;
wherein said fixer material comprises cationic polymers and at least one marker composition soluble in the fixer material and detectable under either ultraviolet or near IR light.
Furthermore, the present invention relates to a cationic polymeric fixer material comprising cationic polymers and at least one marker composition soluble in the fixer material and detectable under either ultraviolet or near IR light.
Additionally, the present invention relates to a method of inkjet printing on a media substrate, comprising:
a) inkjet printing an ink comprising an anionic colorant onto the media substrate;
b) either underprinting before step a) or overprinting after step a) a cationic polymeric fixer material onto the media substrate;
wherein said cationic polymeric fixer material comprises cationic polymers and at least one marker composition soluble in the fixer material and detectable under either ultraviolet or near IR light.